The present invention relates to a rubber composition for tire tread having compatibility between low fuel consumption and abrasion resistance, especially abrasion resistance under severe condition.
Recently a tire for low fuel consumption has been developed by decreasing rolling resistance to meet a demand for low fuel consumption of vehicle for prevention of global warming. In order to decrease the rolling resistance, it is general to lower hysteresis of a rubber composition for tire tread. As one of the method solving thereof, there are a method of decreasing an amount of carbon black as a reinforcing agent in a rubber composition for a tire and a method of substituting silica for carbon black as a reinforcing agent.
However, in tread of a heavy duty tire employed for a truck or bus tire, the abrasion resistance becomes remarkably low with decreasing an amount of carbon black. And it is a problem that a tire obtained by employing silica is low in abrasion resistance under severe condition.
As one of measures, there have been investigated a method of changing a vulcanizing accelerator or increasing an amount of a vulcanizing accelerator. But they are not sufficient, since there arises a problem that rubber property after vulcanization changes.
As the other measure, carbon black surface-treated with silica has been developed, wherein silica adheres to carbon black and the carbon black has characteristics of both carbon black and silica as fillers, and there was disclosed a rubber composition for tire tread obtained by mixing the surface-treated carbon black with a rubber component in Japanese Patent No. 2788212 specification, but there is a problem that the performance thereof is not sufficient.
In order to solve the above-mentioned problems, in case of the surface-treated carbon black used in the composition described in the above-mentioned publication, it is thought that the effect obtained by employing the carbon black was not sufficiently revealed, since the surface of carbon black was coated with silica, an active point of the carbon black was lost, and the property thereof was approximately equal to that in sole use of silica.
Therefore, the effect thereof is thought to be more effective than the carbon black surface-treated silica, if the carbon black is employed, wherein carbon black and silica are three-dimensionally mixed in one particle and the surface of the particle has two regions of silica region and carbon black region.
According to the above-mentioned views, it has been found out to prepare a tire having compatibility between low fuel consumption and abrasion resistance under severe condition by adding a prescribed amount of carbon black containing silica, wherein the silica is three-dimensionally entangled with carbon black in one particle, to a rubber composition for tire tread, particularly tread for a truck or bus tire under severe running condition.
Namely, the present invention relates to a rubber composition for tire tread comprising 100 parts by weight of a rubber component, 10 to 55 parts by weight of carbon black containing silica and 2 to 8% by weight of a silane coupling agent based on the carbon black containing silica.
The rubber composition for tire tread, which comprises 5 to 50 parts by weight of carbon black, wherein a total amount of the carbon black and the carbon black containing silica is 40 to 60 parts by weight,
The rubber composition for tire tread, which comprises 5 to 50 parts by weight of silica, wherein a total amount of the silica and the carbon black containing silica is 40 to 60 parts by weight and an amount of the silane coupling agent is a total amount of 2 to 8% by weight based on the carbon black containing silica and 6 to 12% by weight based on the silica,
A heavy duty tire, which is obtained by employing the rubber composition for tire tread,
The rubber composition for tire tread, which comprises 5 to 50 parts by weight of carbon black and silica, wherein a total amount of the carbon black, the silica and the carbon black containing silica is 40 to 60 parts by weight and an amount of the silane coupling agent is a total amount of 2 to 8% by weight based on the carbon black containing silica and 6 to 12% by weight based on the silica, and
A heavy duty tire, which is obtained by employing the rubber composition for tire tread.